Limonene, pinene, or other terpenes and their alcohols, aldehydes and ketones, as polymer solvents for conducting polymers in coating formulations and their uses

ABSTRACT

A low-VOC (volatile organic compound) and/or low-toxicity coating formulation, including at least one non-halogenated organic solvent including any terpene or terpenoid, and at least one conducting polymer, electroactive polymer and/or conjugated polymer. In another embodiment, the present invention includes a low-VOC (volatile organic compound) and/or low-toxicity coating formulation, including about 0.001% wt. to about 99.9% wt. of at least one non-halogenated organic solvent including a terpene or terpenoid, about 0.01% wt. to about 90% wt. of at least one conducting polymer, and about 0.001% wt to about 90% wt. of at least one surfactant.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) and is acontinuation of U.S. patent application Ser. No. 10/714,296 filed Nov.14, 2003, now abandoned, and is hereby incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The invention described herein may be manufactured and used by or forthe government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

FIELD OF THE INVENTION

The present invention relates to coating formulations including terpenesor terpenoids and their alcohols as organic solvents with conductingpolymers, and more specifically, the use of terpenes to permit polymerincorporation into non-toxic or low-toxicity, non-VOC (Volatile OrganicCarbons) or low-VOC formulations for various military, commercial, andrecreational applications.

BACKGROUND OF THE INVENTION

Terpenes are natural solvents existing both in the citrus fruits and inmany other plants, with extraordinary technical and chemical properties.Terpenes include any hydrocarbon of the formula C₁₀H₁₆ and are derivablechiefly from essential oils, resins, and other vegetable aromaticproducts. Many terpenes are acyclic, bicyclic, or monocyclic, and differsomewhat in physical properties. They can represent an optimalalternative to halogenated solvents in many civil and industrialapplications.

Nearly all the terpenes, contained in the essential oils of many plants,are constituted by a skeleton of carbon atoms made of isoprene unitsregularly linked according with the head-tail position. Some componentsare shown in the following formulas. The main component of the essentialcitrus fruit oil is D-limonene, commonly called dipentene, that is ahydrocarbon insoluble in water; when the essential oils are used toflavor something, it's necessary to bring them in as a very thinsuspension in the aqueous product (soft drinks, juices, etc.). Terpenesare environmental compatibility and can reduce evidently theenvironmental impact in many applications related to the organic solventuse.

U.S. Pat. No. 5,814,376 issued on Sep. 29, 1998 to Michael D. Cabelliteaches a gravure coating process for producing electroconductivepolymer films. Coating is for use in sensors detecting analytes and thefinal product is heated. The above patent is limited to a ribbon-like orflat substrate application. The above uses a conductive polymer andexposing it to a dopant thereby changing its properties in situ. Bychanging it's properties they teach it can be used as a component in ameasuring device. This patent does not teach the use of terpenes withconductive polymers for corrosion inhibition. Ideally, in the presentinvention, once used or applied, the polymer will not be changed,modified or doped. The polymer will continue to perform (preventcorrosion) if it remains in a constant state. While the mechanism forcorrosion protection/inhibition has not been proven for conductivepolymers, it is likely to be a passivation of the metal substrate or anability to allow electron transfer between the coating and substrate toprevent localized charge buildup at a metal surface, which causescorrosion. By preventing a localized charge buildup at a metal surfaceor between two surfaces that have different oxidation potentials, it'slikely that the conductive polymer inhibits the oxidation of metal andtherefore the formation of corrosion products.

U.S. Pat. No. 5,932,643 issued on Aug. 3, 1999 to Frank J. Kenny teachescoating formulations and thermal transfer ribbons that form printedimages containing conductive polymers. The formulations and ribbonsinclude wax, polymer resins, a sensible material and optionally solvent.The above is teaching the polymer coatings for their thermal transferproperties. They teach utilizing toxic organic solvents, which have beenused for conductive polymers long before this patent was issued.However, no terpenes or terpenoids are taught for use in this patent.

If paint formulations use limonene, pinene, or other terpenes (orterpenoids), as a solvent in a waterborne coating application instead oftraditional high-VOC (volatile organic compound) solvents, it willprovide a low-VOC coating application. There is currently no non-toxic,non-chrome, non-metallic containing coating formulation approved formilitary application. From the foregoing, it will be appreciated thatthere is a need in the art for organic terpene based solvent/conductingpolymer coating compositions, which is environmentally safe for varioustypes of military and commercial applications. The present invention isdirected to overcoming one, or more, of the problem set forth above.

SUMMARY OF THE INVENTION

The present invention relates to low-VOC (volatile organic compound)and/or low-toxicity coating formulations, including at least onenon-halogenated organic solvent including any terpene or terpenoid andat least one conducting polymer, electroactive polymer and/or conjugatedpolymer. In another embodiment, the present invention includes a low-VOC(volatile organic compound) and/or low-toxicity coating formulation,including about 0.001% wt. to about 99.9% wt. of at least onenon-halogenated organic solvent including a terpene or terpenoid, about0.01% wt. to about 90% wt. of at least one conducting or electroactivepolymer, and about 0.001% wt to about 90% wt. of at least onesurfactant.

The terpene or terpenoid includes at least one of dipentene(d-limonene), α-pinene, β-mircene, p-cimene, citronellolio, geraniale(citrale), nerol, beta-carotene, menthol, geraniol, farnesol, phytol,their homologs, derivative, enantiomers, isomers includingconstitutional isomers, stereoisomerisms, regioisomers, and geometricisomers, and any combination thereof. The conducting polymers include atleast one of poly[bis(2,5-(N,N,N′,N′-tetraalkyl)amino)-1,4-phenylenevinylene] (BAMPPV) andpoly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEHPPV),polyphenylene vinylenes, polythiophenes, polypyrroles, polyanilines,polyacetates, polyacetylenes, polyacrylates, polyazene, polystyrene,poly-N-vinylcarbazole, polyvinylpyridine, polyindole, and anycombination thereof. The conducting (including electroactive orconjugated) polymers are in neutral, oxidized or reduced form, in theform of a salt including an emeraldine salt, or in any basic or acidicform.

The present invention is used with a broader range of applicationmethods, particularly, spray coating and dip coating. These methods arethe most useful for industry and the military on large substrates andsubstrates with complex geometries (crevices or holes that are hard toaccess) including aircraft and vehicle components.

It is to be understood that the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not to be viewed as being restrictive of the present invention, asclaimed. These and other objects, features and advantages of the presentinvention will become apparent after a review of the following detaileddescription of the disclosed embodiments and the appended claims.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

The present invention relates to low-VOC (volatile organic compound)and/or low-toxicity coating formulations, including at least onenon-halogenated organic solvent including any terpene or terpenoid andat least one conducting polymer, electroactive polymer and/or conjugatedpolymer. In another embodiment, the present invention includes a low-VOC(volatile organic compound) and/or low-toxicity coating formulation,including about 0.001% wt. to about 99.9% wt. of at least onenon-halogenated organic solvent including a terpene or terpenoid, about0.01% wt. to about 90% wt. of at least one conducting or electroactivepolymer, and about 0.001% wt to about 90% wt. of at least onesurfactant.

The following terpenes or terpenoids are constituted by a skeleton ofcarbon atoms made of isoprene unities regularly linked according withthe head-tail position. The terpene or terpenoid includes at least oneof dipentene (d-limonene), α-pinene, β-mircene, p-cimene, citronellolio,geraniale (citrale), nerol, beta-carotene, menthol, geraniol, farnesol,phytol, their homologs, derivative, enantiomers, isomers includingconstitutional isomers, stereoisomerisms, regioisomers, and geometricisomers, and any combination thereof. For example, Aldrich produceslimonene in various optically active isomers and in a technical gradecalled “dipentene.” Terpenes also function as stand-alone solvents or asco solvents. As a solvent or co solvent, a terpene will act as a vehiclefor application of polymers (conductive or nonconductive) or conjugatedpolymers onto substrates. Terpenes function as alternative solvents forpolymers, including conductive or electroactive polymers and conjugatedpolymers, to replace more traditional, more toxic solvents including butnot limited to xylenes, tetrahydrofuran (THF), benzene,n-methylpyrrolidinone (NMP), methylene chloride, and other organicsolvents.

Conjugated polymers have a framework of alternating single and doublecarbon-carbon (sometimes carbon-nitrogen) bonds). Conjugated polymersare polyunsaturated compounds in which all backbone atoms are sp- orsp²-hybridized. For the purposes of the present invention, the termsconductive, electroactive, and conjugated will be interchangeablyutilized throughout. The conducting polymers include at least one ofpoly [bis(2,5-(N,N,N′,N′-tetraalkyl)amino)-1,4-phenylene vinylene](BAMPPV) and poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene](MEHPPV), polyphenylene vinylenes, polythiophenes, polypyrroles,polyanilines, polyacetates, polyacetylenes, polyacrylates, polyazene,polystyrene, poly-N-vinylcarbazole, polyvinylpyridine, polyindole, andany combination thereof. The conducting (including electroactive orconjugated) polymers are in neutral, oxidized or reduced form, in theform of a salt including an emeraldine salt, or in any basic or acidicform. The terpene or terpenoid solvent and conducting polymerformulations are in the form comprising a solution, mixture, suspension,or emulsion. All terpenes, terpenoids, and polymers would ideally benon/low toxic and low VOC.

In other embodiments the coating formulations further include at leastone of surfactant(s), H₂O, and other organic components. Triton X100 isa surfactant utilized in embodiments of the present invention; however,any surfactant commercially available will suffice that includes thefollowing characteristics. The definition of a surfactant orsurface-active agent (Random House) is “any substance that whendissolved in water or other aqueous solution reduces the surface tensionor interfacial tension between it and another fluid.” The idea of asurfactant is to have different functionalities on the same molecule.This will enable two different types of molecules to be somewhatmiscible that normally would not be. The Triton X100 has a similarstructure (carbon ring) to the polymer and the ether alcohol portion issimilar to water (polar) so that the water and polymer may be somehowclosely associated to form a suspension or solution rather thanseparating into two layers like oil and water.

In embodiments of the present invention, terpene and polymer solutions,mixtures, suspensions, or emulsions are added to organic coatingsystems. Above combinations are used to incorporate a polymer into anorganic or inorganic coating or resin, including but not limited toepoxies, polyurethanes, and polyesters. In embodiments of the presentinvention, organic resin includes, but is not limited to polyamides,phenolics, polypropylenes, and polyethylenes. The present coatingformulations can be applied to a substrate including, but not limited tospray coating, dip coating, spin-coating, flow-coating, doctor bladecoating, or screen-printing. The substrates include plastic, rubber,metal, metallic and like surfaces. Embodiments of the present inventioncan be utilized for corrosion protection as replacements for hexavalentchrome.

The present invention will now be explained with references to thefollowing non-limiting experiments.

Experimental Results

A series of terpene polymer solvent samples were prepared and analyzed.In the first experiment, approximately 5.6 mL of dipentene (d-limonene)(Aldrich) was added to beaker “A” with 0.0112 g ofpoly[bis(2,5-(N,N,N′,N′-tetraalkyl)amino)-1,4-phenylene vinylene](BAMPPV). The results had shown that BAMPPV was slightly soluble almostimmediately in the dipentene. The terpene/BAMPPV mixture was stirred andwarmed on low. The BAMPPV polymer was solubilized in solution after 25minutes.

In the second experiment, approximately 5.6 mL of α-pinene (Aldrich) wasadded to beaker “B” with 0.0103 g of BAMPPV. The results shown that theBAMPPV polymer was not immediately soluble in the α-pinene terpene as inthe first experiment utilizing dipentene. The dipentene/BAMPPV andα-pinene/BAMPPV solutions were separately allowed to stir overnight. Inthe first experiment, the BAMPPV was completely dissolved in thedipentene solvent. In the second experiment, the BAMPPV was almostcompletely dissolved in the α-pinene solvent; however, a small amount ofsolids were remaining. These experiments have shown that the solubilityof the BAMPPV polymer in α-pinene is far greater than in xylenes andTHF. Previous solutions trying to dissolve BAMPPV in xylenes and THF hadshown a solubility factor not greater than 0.1%. Solutions of BAMPPV indipentene have been made with 5% wt. polymer (order of magnitudedifference) and have been applied to metal substrates for testing.Higher concentrations are possible.

In the second experiment, 1 mL of water was further added to beaker “B”containing the α-pinene/BAMPPV solution and was stirred to form asuspension. Water was added in order to form a waterborne coating. Anideal formulation would contain as much polymer as possible (referred toas high solids loading) and as little solvent as possible. Since wateris nontoxic and inexpensive compared to any other solvent(environmentally friendly terpene or not), maximizing the polymercontent, water content and minimizing any organic solvent and surfactantis the goal here. One possible exception to the idea of minimizingorganics in a coating application would be the formation of azeotropes.If an organic solvent or surfactant (ideally environmentally benign) isa component in a waterborne formulation and it forms an azeotrope withwater or any other cosolvent that would be removed from the dryingprocess, it may help decrease drying time. Most solvent-based coatingsare desirable from an application standpoint because they are fastdrying compared to waterborne formulations, in general. If an azeotropehas a lower boiling point and/or faster drying time than eithercomponent individually, drying time can often be reduced. Faster drytimes for military and commercial applications, decreases “downtime” ortime in which a system may be inoperable. All components in thespecified coating system can be balanced (ratios adjusted) to makemultiple formulations for different conditions in which they may beused. For example, a coating used in a consistently humid environmentmay have a different water and/or solvent concentration (or anyvariation of any constituent) as compared to a coating that will be usedin an arid environment for drying/curing time reasons. Another reason tovary constituent concentrations would be user specification of thephysical properties of the coating. For example, one user may want alimited amount of conductive polymer whereas another user may want themaximum amount possible for a certain application. Weight of materialsmay factor into a coating formulation as well. Conductive polymers canfunction as coatings alone for certain applications or they may beadditives within other bulk coating systems, such as epoxies, urethanes,polyesters or any bulk resin system. By limiting the weight of aconductive polymer (or weight percent) within a coating, to a minimumamount to achieve desired coating properties, the overall coating weightcan be adjusted. Coating weight is of particular interest for flightapplications.

In a third experiment, a 1% solution was made with 0.4338 g of BAMPPVand 42.95 g of dipentene. The solution in the third experiment was usedfor smaller test vial experiments. Smaller tests were done usingdifferent surfactants to evaluate their respective performance in thecoating formulation. Ideally, a surfactant that can give the desiredresults in the smallest quantity possible is the most useful from anenvironmental and economic point of view, assuming it's low ornon-toxic, of course.

In a fourth experiment, a vial of 9.904 g of dipentene was added to0.1004 g of BAMPPV. The dipentene/BAMPPV solution was further diluted to0.5% by adding 10.33 g of dipentene. A few milliliters of water wereadded to form a suspension. After sitting for an hour, a separation wasobserved. Then 2 drops of Triton-X100 (a surfactant) was added and themixture was stirred for approximately 1 minute and an excellentsuspension resulted. The composition remained in a suspension for a fewdays. After one week, separation was observed. Upon mixing the solutionagain for a few minutes, the suspension was again observed. The vial wasthen allowed to sit without stirring. The suspension was observed to bestable for at least 5 hours. Due to the concentrations of water andweight of Triton-X100 not being precisely measured, this experimentneeded to be repeated.

In the fifth and sixth experiments, compositions including BAMPPV indipentene were added with different surfactants to observe thesurfactant performance. The surfactants were obtained from OsiSpecialties (Greenwich, Conn.) including A1100(gamma-aminopropyltriethoxysilane), A 1101(gamma-aminopropyltriethoxysilane) technical grade, A1170(bis-(gamma-triethoxysilypropyl)amine), and Y9669(n-phenyl-gamma-aminopropyltrimethoxysilane). These additionalsurfactants were compared to the Triton-X100 (polyoxyethylene (10)isooctylcyclohexylether also known as alkylaryl polyether alcohol).

Further experiments were also performed to determine terpene use withconducting polymers. Vial 1: 44.0170 g of dipentene was added to 0.4408g of polymer for a 1% solution. Vial 2: 16.9421 g of dipentene was addedto 0.3369 g of polymer for a 2% solution. Vial 3: 16.9133 g of dipentenewas added to 0.5076 g of polymer for a 2.9% solution. Vial 4: 4.9960 gof DI water was added to 4.2717 g of the 1% solution. Then 3 drops ofTriton X100 (1 drop=0.0249 g) was added to the vial. After addition of 3drops Triton X100, slight separation was noted at bottom, clearer layeron bottom (not completely clear). Vial 5: 2.0447 g of DI water was addedto 4.3224 g of the 1% solution. Then 1 drop of Triton X (5 drop=0.0249g) was added to the vial. Vial 6: 1.910 g of DI water was added to4.2712 g of the 1% solution. Then 3 drops of Triton X (5 drop=−0.0249 g)was added to the vial. Vial 7: 1.9773 g of DI water was added to 4.3381g of the 1% solution. Then 2 drops of Triton X (5 drop=0.0249 g) wasadded to the vial.

The results of the above experiments are as follows: 1%polymer/dipentene solution: 1.0005 g of polymer added to 98.9992 g ofdipentene. Did not go completely into solution when stirred overnight,so heated and let stir overnight again. Vial A: 1.0245 g of water wasadded to 5.0468 g of limonene/polymer solution. 0.2693 g of Triton X100was then added. Vial B: 3.0188 g of water was added to 5.0421 g oflimonene/polymer solution. 0.2630 g of Triton X100 was then added. VialC, 5.0184 g of water was added to 5.0455 g of limonene/solution. 0.2491g of Triton X100 was then added.

Vial D: 0.2462 g of Triton X100 was added to 5.0477 g oflimonene/polymer solution. 1.0349 g of water was added to the limoneneand Triton X100. Vial E: 0.2845 g of Triton X was added to 5.0493 g oflimonene/polymer solution. 3.0154 g of water was added to the limoneneand Triton X100. Vial F: 0.2620 g of Triton X was added to 5.0233 g oflimonene/polymer solution. 5.0168 g of water was added to the limoneneand Triton X100. When adding water after Triton X, a precipitate formedon the bottom of the vial more often than when water was added beforeTriton X. But, after stirring for a while, both group ABC and group DEFstarted to look the same. Vials A and D look good, but some initialseparation was noticed in B, C, E, and F.

Additional terpenes and conducting polymers experiments were performedwith the following results. Vial G: 1.7914 g of dipentene was added to0.0200 g of Poly(3-hexylthiophene-2,5-diyl) regiorandom. Vial H, 1.8051g of pinene was added to 0.0200 g of Poly(3-hexylthiophene-2,5-diyl)regiorandom. Vial I: 1.8015 g of dipentene was added to 0.0207 g ofMEH-PPV. Vial J: 1.8053 g of pinene was added to 0.0218 g of MEH-PPV.Vial K: 1.8004 g of dipentene was added to 0.0261 g ofPoly(3-hexylthiophene-2,5-diyl) regioregular. Vial L: 1.8024 g of pinenewas added to 0.0226 g of Poly(3-hexylthiophene-2,5-diyl) regioregular. Hand G are fully soluble, K and L are mostly soluble, and I and J aremostly soluble. 24 hours later, all vials appear in the same conditionall the previous day. The solutions from vials G through L were filteredwith Whatman 0.2 micron syringe filters to remove any remaining solids.The solutions were then used in waterborne formulations. The solutionswere filtered into new vials with designations 38A, 38B, 38C, 38D, 38E,and 38F corresponding to vials G, H, I, J, K and L, respectively. Onedrop of Triton X100 was added to each vial and the contents stirred.Visual results were as follows: 38A was in solution after about 20seconds. 38B was in solution after about 30 seconds. 38C and 38D were insolution after about 25 seconds. 38E and 38F were in solution for a fewseconds and the separation occurred. 38A, 38B, 38C and 38D stayed insolution after a total of 2 drops of Triton X100 was added. After 2minutes, mixtures of 38B and 38D began to separate. After 2 min 30seconds mixtures 38A and 38C began to separate. Optimum ratios andstirring conditions are being established.

Embodiments of the present films are included, but not limited to thefollowing uses: light-emitting devices, photovoltaic cells, capacitors,super capacitors, devices for sensor protection against lasers, devicesfor optical switching and modulating, corrosion protection, adhesives,electromagnetic shielding (EMI), anti-biofouling, camouflage, chemicalsensors. The use of terpenes or terpenoids to act as a solvent orco-solvent will permit the dispersion of a conducting polymer(s) into asolution, suspension, emulsion, or mixture. Embodiments of the presentinvention including conductive polymers are used to reduce or inhibitcorrosion in organic coatings when applied to plastic, rubber, metalsubstrates, or their interfaces.

Coatings including the present invention terpene/conducting polymerformulations are used as low-VOC (volatile organic compound) and/orlow-toxicity coatings for items including but not limited to aircraft,vehicles, ground equipment, structures and architectural components.Low-VOC coatings are desirable since they should exhibit low-VOCemissions into the atmosphere and reduce hazardous materials exposure tothose personnel that apply, repair, or remove such coatings. Thecoatings of the present invention would be amenable but not limited toapplications on aircraft or ship hardware in compliance with State andFederal environmental regulations.

It should be understood that the examples and embodiments describedherein are for illustrative purposes only and that various modificationsor changes in light thereof will be suggested to persons skilled in theart and are to be included within the spirit and purview of thisapplication and the scope of the appended claims.

1. A method for passivating a metallic surface comprising: providing ametallic surface; selecting at least one solvent from the group ofterpenes; selecting at least one polymer from the group ofpoly[bis(2,5-(N,N,N′,N′-tetraalkyl)amino)-1,4-phenylene vinylene]polymers; solubilizing said at least one polymer in said at least onesolvent to form a polymeric composition; contacting the metallic surfacewith the polymeric composition to form a passivating region.
 2. A methodfor making a passivating layer comprising: providing a metallic surface;selecting at least one solvent from the group of terpenes; selecting atleast one polymer from the group ofpoly[bis(2,5-(N,N,N′,N′-tetraalkyl)amino)-1,4-phenylene vinylene]polymers; solubilizing said at least one polymer in said at least onesolvent to form a polymeric composition; contacting the metallic surfacewith the polymeric composition to form a passivating layer on themetallic surface.
 3. The method of claim 1 or claim 2 wherein said atleast one solvent is selected from the group of terpenoids.
 4. Themethod of claim 1, claim 2 or claim 3 wherein said group ofpoly[bis(2,5-(N,N,N′,N′-tetraalkyl)amino)-1,4-phenylene vinylene]polymers is replaced by the group of poly(3-hexylthiophene-2,5-diyl)regiorandom polymers.
 5. The passivating layer formed by the method ofclaim 2.